Alkylation process unit comprising a fractionation unit for separating hydrogen gas and hydrogen chloride

ABSTRACT

We provide an alkylation process, comprising: separating and recycling a hydrogen gas and a hydrogen chloride from an offgas of a hydrogenation reactor; wherein the hydrogen gas is recycled to the hydrogenation reactor; and wherein the hydrogen chloride is recycled to an alkylation reactor. We also provide an alkylation process unit for performing this process.

This application is a divisional of U.S. application Ser. No.13/563,385, titled “HYDROGEN RECYCLE AND HYDROGEN CHLORIDE RECOVERY INAN ALKYLATION PROCESS”, which was filed on Jul. 31, 2012, hereinincorporated in its entirety.

This application is a continuation of U.S. application Ser. No.13/563,355, titled “ALKYLATION PROCESS WITH RECYLE OF HYDROGEN ANDRECOVERY OF HYDROGEN CHLORIDE”, which was filed on Jul. 31, 2012, hereinincorporated in its entirety.

This application is a continuation of U.S. application Ser. No.13/563,415, titled “EXTRACTED CONJUNCT POLYMER NAPHTHA”, which was filedon Jul. 31, 2012, herein incorporated in its entirety.

This application is a continuation of U.S. application Ser. No.13/901,935, titled “ALKYLATION PROCESS UNIT WITH RECYCLE OF HYDROGEN ANDRECOVERY OF HYDROGEN CHLORIDE”, which was filed on May 24, 2013, hereinincorporated in its entirety.

TECHNICAL FIELD

This application is directed to a process and process unit for improvedhydrogen chloride and hydrogen recycling in an alkylation process usinghydrogenation.

BACKGROUND

Improved processes and process units for recycling hydrogen and hydrogenchloride are desired in alkylation processes using hydrogenation.

SUMMARY

This application provides an alkylation process, comprising: separatingand recycling a hydrogen gas and a hydrogen chloride from an offgas of ahydrogenation reactor; wherein the hydrogen gas is recycled to thehydrogenation reactor; and wherein the hydrogen chloride is recycled toan alkylation reactor.

This application also provides an alkylation process unit, comprising:

a. a fractionation unit for separating a hydrogen gas and a hydrogenchloride from an offgas of a hydrogenation reactor that regenerates aused ionic liquid catalyst; and

b. a first connection between the fractionation unit and thehydrogenation reactor for transmitting at least a portion comprising thehydrogen gas to the hydrogenation reactor; and

c. a second connection between the fractionation unit and an alkylationreactor to transmit at least a second portion comprising the hydrogenchloride to the alkylation reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an alkylation process unit with catalysthydro-regeneration, hydrogen recycle and hydrogen chloride recovery; thecomprehensive case.

FIG. 2 is a diagram of an alkylation process unit with catalysthydro-regeneration, hydrogen recycle, and hydrogen chloride removal bycaustic scrubbing; the comparison case.

FIG. 3 is a diagram of an alternative alkylation process unit withcatalyst hydro-regeneration, hydrogen recycle from a separator, andhydrogen chloride recovery.

FIG. 4 is a diagram of a second alternative alkylation process unit withcatalyst hydro-regeneration, hydrogen recycle and hydrogen chloriderecovery.

FIG. 5 is a diagram of a third alternative alkylation process unit withcatalyst hydrogenation, hydrogen recycle and hydrogen chloride recovery.This diagram includes a selective olefin isomerization reactor.

FIG. 6 is a diagram of a hydro-regeneration process without hydrocarbonextraction solvent.

DETAILED DESCRIPTION

Alkylation processes and alkylation process units are used to makealkylate products, including alkylated aromatics and alkylatedisoparaffins. The alkylate products can have a broad range of usesincluding, for example, gasoline blending components, middledistillates, base oils, and petrochemical components. The alkylationcatalysts used in these processes for alkylation often contain achloride. Examples of alkylation catalysts are alumina/silica aerogelswith metal chloride (e.g., zinc chloride), and Friedel-Crafts alkylationcatalysts. Friedel-Crafts alkylation involves the alkylation of anaromatic ring or isoparaffin with an alkyl halide or any carbocationicintermediate using a strong Lewis acid catalyst. Examples ofcarbocationic intermediates are those derived from alkenes and a proticacid, Lewis acid, enones, and epoxides. Some ionic liquid catalysts areFriedel-Crafts catalysts.

In an alkylation process employing either reactants or catalystscomprising a chloride, where a hydrogenation reactor provides an offgasto an alkylation reactor, it is often preferred to maintain a desiredlevel of chloride in the process as well as to utilize hydrogenefficiently. ‘Offgas’ is defined herein as a gaseous effluent from thehydrogenation reactor. ‘Recycling’ is defined herein as returningmaterial to a previous stage in a cyclic process. ‘Recovering’ isdefined herein as retaining either in a substantial amount or in full,as opposed to disposing or removing. A substantial amount is at least 50wt %.

In one embodiment, the alkylation reactor uses an alkylation catalystcomprising a chloride.

Because the alkylation process includes a chloride, the hydrogenationunit liberates hydrogen chloride, which can build up to excessive levelsand can suppress conversion in the hydrogenation reactor unless it isremoved. Acid gas treating methods, for example, caustic aqueousscrubbing systems, can be used, but then the hydrogen chloride cannot besimply reused in the alkylation process. One example of how an acid gastreating method could be employed in an alkylation plant is shown inFIG. 3. If sodium hydroxide (NaOH) is used as the caustic reactant, forexample, then the hydrogen chloride (HCl) is converted to sodiumchloride (NaCl) and water, and it is not suitable for recycling into anionic liquid alkylation process. The HCl destroyed in the HCl removalstep can represent a significant operating cost when it must becompensated for by additional chloride injection into the alkylationprocess unit. It can also result in an aqueous waste stream that must beneutralized and disposed of in a water treatment system of the facility.Further, the recycle hydrogen must then be thoroughly dried before usein a hydrogenation reactor that uses or regenerates a water reactivecatalyst.

Referring to FIG. 1, it is shown that a hydrogenation reactor (100) canbe used continuously with little to no excessive hydrogen chloride buildup, and with efficient hydrogen use, in an alkylation process usingeither reactants or catalysts with a chloride by the following process:

-   An effluent from an alkylation reactor (40) is separated into a    portion of the effluent (70) and alkylate products (80). The portion    of the effluent (70) is hydrogenated in a hydrogenation reactor    (100). The hydrogenation reactor (100) produces a hydrogenated    effluent (10) which is separated in a separator (400) into an offgas    (50) and an ionic liquid catalyst stream (60). The offgas comprises    hydrogen gas and hydrogen chloride. The ionic liquid catalyst stream    (60) is optionally recycled to the alkylation reactor (300). The    offgas (50) from the hydrogenation reactor (100), is separated in a    fractionation unit (200) into a gas fraction comprising a hydrogen    gas (20) and a light hydrocarbon fraction comprising a hydrogen    chloride (30). At least a portion of the gas fraction comprising the    hydrogen gas (20) is recycled to the hydrogenation reactor (100) and    at least a portion of the light hydrocarbon fraction comprising    hydrogen chloride (30) is recycled to the alkylation reactor (300).

FIG. 2 shows a comparison process unit that does not recover a lightfraction comprising a hydrogen chloride. In FIG. 2, hydrogen (90), and aportion of the effluent (70) comprising used catalyst from an alkylationreactor (300) is regenerated in a hydrogenation reactor. Thehydrogenated effluent (10) is separated in a separator (400) that is agas/liquid separation unit. The offgas (50) from the separator issubsequently treated in a caustic treating unit (600) and a drier (700),which remove the hydrogen chloride (as opposed to recovering) to producea dry gas fraction comprising a hydrogen gas (20). The gas fractioncomprising the hydrogen gas (20) is sent to the hydrogenation reactor. Arecycle gas purge (15) stream removes excess hydrogen and lighthydrocarbons from the process unit. The separated liquid (85) from theseparator is mixed with a hydrocarbon extraction solvent (25) and themixture is fed to an ionic liquid catalyst and hydrocarbon separator(500) which separates the mixture into a stream comprising both conjunctpolymer and extraction solvent (35) and an ionic liquid catalyst stream(60). The stream comprising both conjunct polymer and extraction solvent(35) is sent to the refinery hydrocarbon pool of alkylate products (80).The ionic liquid catalyst stream (60) is recycled to the alkylationreactor (300). Chloride addition (95) is needed to replace the hydrogenchloride that is removed in the caustic treating unit (600).

FIG. 3 shows an improved process compared to FIG. 2, wherein hydrogen isrecycled and hydrogen chloride is recovered and recycled efficiently. InFIG. 3, hydrogen (90), and a portion of the effluent (70), comprisingused catalyst, from an alkylation reactor (300) are regenerated in ahydrogenation reactor. The hydrogenated effluent (10) is separated in aseparator (400) that is a gas/liquid separation unit. A hydrocarbonextraction solvent (25) is fed to the separator (400) such that theseparator (400) produces a separated liquid (85) and a gas fractioncomprising a hydrogen gas (20). The gas fraction comprising the hydrogengas (20) has a reduced amount of hydrogen chloride and the gas fractioncomprising the hydrogen gas (20) is recycled to the hydrogenationreactor (100). The separated liquid (85) from the separator (400)comprises a hydrogen chloride. The separated liquid (85) is fed to anionic liquid catalyst and hydrocarbon separator (500), which separatesthe separated liquid (85) into a hydrocarbon stream (52) and an ionicliquid catalyst stream (60). The hydrocarbon stream (52) is fed to afractionation unit (200), where it is separated into two streams. Onestream is a light hydrocarbon fraction comprising the hydrogen chloride(30). The second stream is extracted conjunct polymer naphtha (45). Thelight hydrocarbon fraction comprising the hydrogen chloride (30) is alsorecycled to the alkylation reactor (300). In this process the hydrogenchloride is recovered and recycled, rather than removed, as in FIG. 2.The extracted conjunct polymer naphtha (45) is sent to the refineryhydrocarbon pool of alkylate products (80).

FIG. 4 shows an alternative process wherein hydrogen is recycled andhydrogen chloride is recovered and recycled. In FIG. 4, hydrogen (90),and a portion of the effluent (70) comprising used catalyst from analkylation reactor (300) are fed to a hydrogenation reactor (100). Thehydrogenated effluent (10) from the hydrogenation reactor (100) is fedto a separator (400), which separates the hydrogenated effluent (10)into an offgas (50) and a separated liquid (85). The offgas (50) is fedto a fractionation unit (200). A hydrocarbon extraction solvent (e.g.,an isoparaffin feed to the alkylation reactor) is also fed to thefractionation unit (200). The fractionation unit (200) fractionates theoffgas (50) into a gas fraction comprising the hydrogen gas (20) and alight hydrocarbon fraction comprising a hydrogen chloride (30). The gasfraction comprising the hydrogen gas (20) is recycled to thehydrogenation reactor (100). The light hydrocarbon fraction comprisingthe hydrogen chloride (30) is recovered and recycled to the alkylationreactor. The separated liquid (85) from the separator (400) is mixedwith a conjunct polymer extraction solvent (55) and the mixture is fedto an ionic liquid catalyst and hydrocarbon separator (500). The ionicliquid catalyst and hydrocarbon separator (500) separates the mixture ofthe separated liquid (85) and conjunct polymer extraction solvent (55)into extracted conjunct polymer naphtha (45) and an ionic liquidcatalyst stream (60). The extracted conjunct polymer naphtha (45) issent to the refinery hydrocarbon pool of alkylate products (80). Theionic liquid catalyst stream is recycled to the alkylation reactor(300).

FIG. 5 shows another alternative process wherein hydrogen is recycledand hydrogen chloride is recovered and recycled. In FIG. 5, a portion ofthe effluent (70) comprising used catalyst from an alkylation reactor(300) and optionally, hydrogen (90) are fed to a hydrogenation reactor(100). The hydrogenated effluent (10) from the hydrogenation reactor(100) is fed to a separator (400), which separates the hydrogenatedeffluent (10) into an offgas (50) and a separated liquid (85). In oneembodiment, hydrogen (90) is not separately fed to the hydrogenationreactor (100), as all of the hydrogen needs for hydrogenation aresupplied by a gas fraction comprising a hydrogen gas (20) from afractionation unit (200). The offgas (50) is fed to the fractionationunit (200). Hydrogen (90) and an olefin feed (75) (e.g., 1-butene) arefed to a selective olefin isomerization reactor (800), wherein theolefin feed (75) is converted to isomerized olefins (12) (e.g.,2-butene). A hydrocarbon extraction solvent (25) (e.g., an isoparaffinfeed (65) to be alkylated in the alkylation reactor) is mixed with theisomerized olefins (12) and the mixture is fed to the fractionation unit(200). The fractionation unit (200) fractionates the offgas (50) into agas fraction comprising the hydrogen gas (20) and a light hydrocarbonfraction comprising a hydrogen chloride (30). The gas fractioncomprising the hydrogen gas (20) is recycled to the hydrogenationreactor (100). Excess hydrogen and light hydrocarbons are removed in arecycle gas purge (15). The light hydrocarbon fraction comprising thehydrogen chloride (30) is recovered and recycled to the alkylationreactor. The separated liquid (85) from the separator (400) can be mixedwith a conjunct polymer extraction solvent (55) or an effluent from analkylation reactor (40), (as shown), and the mixture is fed to an ionicliquid catalyst and hydrocarbon separator (500). The ionic liquidcatalyst and hydrocarbon separator (500) separates the mixture of theseparated liquid (85) and one or more of conjunct polymer extractionsolvent (55) and effluent from an alkylation reactor (40) into a streamcomprised of extracted conjunct polymer naphtha (45) and an ionic liquidcatalyst stream (60). The extracted conjunct polymer naphtha (45) issent to the refinery hydrocarbon pool of alkylate products (80). Theionic liquid catalyst stream (60) is recycled to the alkylation reactor(300). As needed, chloride addition (95) can be made to the alkylationreactor (300).

Hydrogenation

Hydrogenation is a reduction reaction which results in an addition ofhydrogen to a starting molecule. Hydrogenation changes the physical andchemical properties of the starting molecule. The addition of hydrogencan cleave the starting molecule, remove undesired impurities (e.g.,sulfur, oxygen, nitrogen, conjunct polymer), or cause the startingmolecule to undergo rearrangement (e.g., isomerization). Hydrogenationis often performed in the presence of a hydrogenation catalyst. One useof hydrogenation is to hydrogenate a used alkylation catalyst, such as aused acidic ionic liquid alkylation catalyst.

In one embodiment, an alkylation catalyst becomes deactivated during useand requires regeneration. The deactivation can be caused by, forexample, the build-up of conjunct polymer in the alkylation catalyst.Regeneration can be achieved in a hydrogenation reactor (also referredto herein as a hydro-regeneration reactor). The hydrogenation removesthe impurities, such as conjunct polymer, from the alkylation catalyst,thus increasing the acidity and ability of the catalyst to performalkylations. In this embodiment, the hydrogenation reactor is used toregenerate the used alkylation catalyst.

In one embodiment, the catalyst used in the alkylation reactor isregenerated in the hydrogenation reactor. The hydrogenation reactorcontacts the used catalyst with hydrogen and typically, a hydrogenationcatalyst to regenerate the alkylation catalyst. In one embodiment, thehydrogenation catalyst is supported.

In one embodiment, the portion of the effluent comprises used catalystwhich can be regenerated in the hydrogenation reactor. In oneembodiment, the hydrogenation reactor contacts the used ionic liquidcatalyst with hydrogen and a hydrogenation catalyst to regenerate theused ionic liquid catalyst. In one embodiment, zeolites or molecularsieves are added to the hydrogenation catalyst to improve the catalyst'sperformance. In one embodiment, the hydrogenation catalyst is supported.Typical support materials for the hydrogenation catalyst are kieselguhr,alumina, silica, and silica-alumina. Other support materials includealumina-boria, silica-alumina-magnesia, silica-alumina-titania andmaterials obtained by adding zeolites and other complex oxides thereto.When used, the support material has adequate mechanical strength andchemical stability at the hydrogenation reaction temperature.

In one embodiment, the hydrogenation is carried out in the presence of acatalyst which usually comprises a metal or non metal hydrogenationcomponent on a porous support material, such as a natural clay or asynthetic oxide. Examples of metal hydrogenation components that can beused are Fe, Co, Ni, Ru, Rh, Pd, Pt, Ir, Os, Cr, Mn, Ti, V, Zr, Mo, W,and mixtures thereof. Examples of non metal hydrogenation components Te,As, and mixtures thereof. The hydrogenation components can be usedsingly or in combination.

The hydrogenation can be carried out over a broad range of hydrogenpressures, typically from about 50 to 5,000 psig. Hydrogenationconditions can include temperatures of −20° C. to 400° C., or 50° C. to300° C.; and total pressures of atmospheric to 5,000 psig, or 50 to2,500 psig. Hydrogenation contact times can be from 0.1 minute to 24hours, such as 10 minutes to 12 hours. Feed to catalyst ratios duringthe hydrogenation can vary from 0.1 to 10 vol/vol/hour. A normalhydrocarbon can optionally be used as a solvent in the hydrogenationreactor.

Examples of hydrogenation of ionic liquid catalysts for regeneration,for example, are given in U.S. Pat. No. 7,691,771, U.S. Pat. No.7,651,970, U.S. Pat. No. 7,678,727, and U.S. Pat. No. 7,825,055.

Separator for Hydrogenated Effluent

In one embodiment, the separator (400) separates the hydrogenatedeffluent, e.g., regenerated catalyst effluent streams, for efficientdownstream processing. The separator can be configured in severaldifferent ways. For example, in FIG. 1, the separator separates theionic liquid catalyst stream (60) from the regenerated catalyst effluentfirst. Then the offgas (50) stream containing hydrogen, hydrogenchloride, and hydrocarbon is sent to a fractionation unit (200) forfurther separation into a gas fraction comprising a hydrogen gas (20)and a light hydrocarbon fraction comprising a hydrogen chloride (30). InFIGS. 2, 4, and 5, the separator separates the regenerated catalysteffluent streams into an offgas (50) comprising hydrogen chloride gasand into a separated liquid (85). In FIG. 3, a hydrocarbon extractionsolvent (25) was added to the separator to facilitate extraction ofhydrogen chloride into a liquid stream. The separator (400) produces agas fraction comprising a hydrogen gas (20), having a reduced level ofhydrogen chloride, and a separated liquid (85). The separated liquid(85), comprising hydrogen chloride, hydrocarbon and ionic liquidcatalyst, is sent to an ionic liquid catalyst and hydrocarbon separator(500). Examples of ionic liquid catalyst and hydrocarbon separators arecentrifuges, liquid-liquid extractor, selective filters, settling tanks,and coalescers. Examples of suitable coalescers are described in U.S.Pat. No. 8,067,656.

Hydrocarbon Extraction Solvent

In one embodiment, the hydrogen chloride is extracted from the offgas ofthe hydrogenation reactor using a hydrocarbon extraction solvent. Thehydrogen chloride can be extracted into the hydrocarbon extractionsolvent, which is transmitted to the alkylation reactor. This embodimentis shown in FIGS. 3 through 5. The hydrocarbon extraction solvent can beany hydrocarbon that can serve as a solvent or reactant for thealkylation process. Examples of suitable extraction solvents foralkylation processes making alkylate gasoline are isobutane, alkylategasoline, isomerized olefin, and mixtures thereof.

In one embodiment the hydrocarbon extraction solvent comprises anisomerized olefin. An example of an isomerized olefin is 2-butene.Processes for isomerizing olefins to make alkylate gasoline withimproved RON are taught in U.S. Pat. No. 7,553,999.

In one embodiment, the hydrocarbon extraction solvent (25) is added tothe hydrogenation reactor (100). In another embodiment, the hydrocarbonextraction solvent (25) is added to the hydrogenated effluent (10). Inyet another embodiment, the hydrocarbon extraction solvent is added toeither the separator (400) or the fractionation unit (200). In oneembodiment, the hydrocarbon extraction solvent is fed into a streamselected from a hydrogenated effluent (10), an offgas (50) from aseparator, or a combination thereof.

In FIG. 3, for example, the hydrocarbon extraction solvent is added tothe hydrogenated effluent (10) either in the separator or prior toseparating. In one embodiment, the effluent from the hydrogenationreactor can be separated by a series of a gas/liquid separator, aliquid/liquid separator, and a fractionation unit that is a distillationcolumn. In one embodiment, the effluent from the hydrogenation reactor(100) is separated by the gas/liquid separator into: a) a gas fractioncomprising a hydrogen gas (20) and b) separated liquid (85). Theseparated liquid comprises a light hydrocarbon fraction comprising ahydrogen chloride (30). In one embodiment, the liquid/liquid separatorremoves one liquid (regenerated alkylation catalyst), which is recycledback to an alkylation reactor, from a second liquid comprising thehydrocarbon extraction solvent and hydrogen chloride. The second liquidcan be distilled in a fractionation unit into at least two streams, onebeing a portion of the light hydrocarbon fraction comprising thehydrogen chloride and the hydrocarbon extraction solvent, and the otherbeing extracted conjunct polymer naphtha. In this example, thehydrocarbon extraction solvent can also be a reactant in the alkylationreactor. In this example, the hydrocarbon extraction solvent can be usedto cool the effluent from the hydrogenation reactor.

The separating of the hydrogen gas and hydrogen chloride can beperformed in a fractionation unit that is a distillation column. Forexample, in FIG. 5, the hydrocarbon extraction solvent comprises anisoparaffin (e.g., isobutane) and isomerized olefin. In this example,the hydrocarbon extraction solvent is mixed with the offgas from thehydrogenation reactor in the fractionation unit, e.g., a distillationcolumn. In one embodiment, the isoparaffin and isomerized olefin are fedto the fractionation unit, used for the separating, at a location abovewhere the offgas of the hydrogenation reactor is fed into thefractionation unit. In other words, the hydrocarbon extraction solventis fed to the fractionation unit at a location above where the hydrogengas and the hydrogen chloride are fed to the fractionation unit. In oneembodiment, the hydrocarbon extraction solvent is fed to thefractionation unit in a counter current to the flow of offgas into thefractionation unit. In this example, and other embodiments, thehydrocarbon extraction solvent comprises an olefin and an isoparaffin.The olefin and the isoparaffin can be alkylated to make an alkylategasoline blending component. In some embodiments, the alkylationcatalyst is a chloroaluminate ionic liquid catalyst.

In one embodiment, the hydrocarbon extraction solvent comprising anolefin and an isoparaffin to be alkylated to make alkylate gasoline hasan amount of isomerized olefin that is greater than 10 wt %, greaterthan 15 wt %, greater than 30 wt %, greater than 40 wt %, greater than50 wt %, greater than 60 wt %, or greater than 70 wt % of the olefin inthe hydrocarbon extraction solvent. For example, to make high RONalkylate gasoline blending component the olefin is greater than 40 wt %,greater than 50 wt %, and up to 100 wt % 2-butene, and the isoparaffinis isobutane.

In one embodiment, the hydrocarbon extraction solvent is fed at avol/vol ratio of the hydrocarbon extraction solvent to the ionic liquidcatalyst from 0.5 to 20.0, from 1.0 to 10.0, or from 1.5 to 5.0. Thevol/vol ratio can be selected to provide the desired level of hydrogenchloride in the gas fraction comprising a hydrogen gas (20). The desiredlevel of hydrogen chloride in the gas fraction comprising the hydrogencan be any level at least 25 wt % lower than a level of hydrogenchloride in the hydrogenated effluent, such as less than 1,000 wppm,less than 600 wppm, 500 wppm or less, less than 200 wppm, or less than100 wppm. Alternatively, the vol/vol ratio can be selected to providethe desired wt % of the hydrogen chloride produced in the hydrogenationreactor that is recovered and recycled to the alkylation reactor. Insome embodiments the desired level of hydrogen chloride in the gasfraction comprising the hydrogen is much reduced, such as at least 50 wt% up to 99% reduced.

Chloride Retention

In one embodiment, at least 80 wt % of the hydrogen chloride produced inthe hydrogenation reactor is recovered and recycled to the alkylationreactor. For example, at least 85 wt %, at least 90 wt %, at least 94 wt%, up to 98 wt % of the hydrogen chloride can be recycled. In oneembodiment, the chloride in the used catalyst is a hydrogen chlorideco-catalyst.

By recycling the chloride, the amount of the chloride that needs to beadded to the process is greatly reduced. Examples of chloride that maybe added to the process to maintain the ionic liquid catalyst activityinclude hydrogen chloride, alkyl chloride, and metal chloride. In oneexample, the chloride added to the process is n-butyl chloride ort-butyl chloride. The chloride added to the process can be added at anypoint in the process, but is usually introduced into the alkylationreactor (300) as either a separate stream, or can be mixed with theionic liquid catalyst stream (60) or the light hydrocarbon fractioncomprising the hydrogen chloride (30).

Hydrogen Recycling

The hydrogen gas is separated and recycled to the hydrogenation reactor.Recycling the hydrogen can save significant cost associated withhydrogen supply. In one embodiment, the process additionally comprisesremoving a recycle gas purge (15) from the effluent from thefractionation unit (200). In one embodiment, the recycle gas purge (15)comprises an excess of the hydrogen gas from the offgas (50) of thehydrogenation reactor. This is demonstrated in FIG. 5. The excesshydrogen from the recycle gas purge (15) can then be utilized in otherparts of an integrated refinery, stored, or used for other purposes. Theremoval of the excess hydrogen gas can eliminate concerns over excessivehydrogen in distillation column overhead systems.

In one embodiment, the process comprises compressing the recycledhydrogen gas in the gas fraction comprising the hydrogen gas (20) beforerecycling it to the hydrogenation reactor (100). The compression, whenused, can use conventional compressor equipment and piping because thegas fraction comprising a hydrogen gas contains limited amounts ofhydrogen chloride, and is thus not highly corrosive.

Separating

In one embodiment, the separating of the hydrogen gas and the hydrogenchloride from the offgas is done in a distillation column. In anotherembodiment, reactants to be alkylated in the alkylation reactor are alsofed into the distillation column used to separate the hydrogen gas andthe hydrogen chloride. This embodiment is shown in FIG. 4. The reactantscan be fed either as a mixture or separately into the distillationcolumn.

In one embodiment, wherein the separating is done in a distillationcolumn into which is fed reactants to be alkylated, the reactants can befed to the distillation column at a location above where the offgas fromthe hydrogenation reactor is fed to the distillation column. In oneembodiment, the reactants to be alkylated, e.g., makeup isobutane andisomerized olefins are fed either separately or combined into thedistillation column.

In one embodiment, shown in FIG. 5, the offgas from the hydrogenationreactor is first separated by a gas/liquid separator into a gas streamcomprising hydrogen and hydrogen chloride and an ionic liquid catalyststream comprising regenerated catalyst and extracted conjunct polymernaphtha. The offgas is mixed with isomerized olefins (e.g., 2-butene)and isobutane in a fractionation unit, where they are distilled into agas fraction comprising the hydrogen gas, and a light hydrocarbonfraction comprising the hydrogen chloride. The light hydrocarbonfraction comprising the hydrogen chloride additionally comprises anisoparaffin (e.g., isobutane), isomerized olefins (e.g., 2-butene) andthe hydrogen chloride, and the light hydrocarbon fraction is recycled tothe alkylation reactor.

In one embodiment, the stream comprising the hydrogen chloride from thedistillation column is mixed with a recycled stream comprising a mixtureof a hydrogen chloride and a propane, from the alkylation reactor,before recycling the mixture back into the alkylation reactor.

In one embodiment, the light hydrocarbon fraction comprising thehydrogen chloride from the distillation column also comprises isobutaneand olefins. This light hydrocarbon fraction can be mixed with arecycled stream from the ionic liquid reactor before recycling themixture back into the alkylation reactor. The recycled stream from theionic liquid reactor can, for example, comprise hydrogen chloride,propane, and isobutane.

Regenerated Alkylation Catalyst

In one embodiment, the hydrogenation reactor is used to regenerate aused alkylation catalyst. In one embodiment, the regenerated alkylationcatalyst is recycled to the alkylation reactor. For example theregenerated alkylation catalyst can be a regenerated ionic liquidcatalyst in the ionic liquid catalyst stream (60). This embodiment,where a regenerated alkylation catalyst that is an ionic liquid catalyststream, is recycled to the alkylation reactor is shown in FIGS. 3, 4,and 5.

In one embodiment, an effluent from the hydrogenation reactor isseparated in a first separator to produce a gas fraction comprising thehydrogen gas and a light hydrocarbon fraction comprising the hydrogenchloride. The gas fraction comprising the hydrogen gas is recycled tothe hydrogenation reactor. The light hydrocarbon fraction is separatedin a second separator to produce a stream comprising a regeneratedalkylation catalyst (an ionic liquid catalyst, for example) and alighter stream comprising one or more reactants, extracted conjunctpolymer naphtha, and hydrogen chloride. The lighter stream is furtherseparated in a distillation column to produce a top cut comprisinghydrocarbon reactants and hydrogen chloride and a bottom cut comprisingextracted conjunct polymer naphtha. The top cut is recycled to thealkylation reactor and the bottom cut is mixed with the alkylationproducts.

Ionic Liquid Catalyst

In one embodiment, the alkylation reactor uses an alkylation catalystthat is an ionic liquid catalyst. The ionic liquid catalyst is any ionicliquid which works effectively to perform an alkylation reaction with achloride as a co-catalyst. The ionic liquid catalyst is an organic saltor mixture of salts. The ionic liquid catalyst can be characterized bythe general formula Q+A−, wherein Q+ is an ammonium, phosphonium,boronium, iodonium, or sulfonium cation and A− is a negatively chargedion such as Cl⁻, Br⁻, ClO₄ ⁻, NO₃ ⁻, BF₄ ⁻, BCl₄ ⁻, PF₆ ⁻, SbF₆ ⁻, AlCl₄⁻, TaF₆ ⁻, CuCl₂ ⁻, FeCl₃ ⁻, HSO₃ ⁻, RSO₃ ⁻, SO₃CF₃ ⁻, alkyl-arylsulfonate, and benzene sulfonate (e.g., 3-sulfurtrioxyphenyl). In oneembodiment the ionic liquid catalyst is selected from those havingquaternary ammonium halides containing one or more alkyl moieties havingfrom about 1 to about 12 carbon atoms, such as, for example,trimethylamine hydrochloride, methyltributylammonium halide, orsubstituted heterocyclic ammonium halide compounds, such ashydrocarbyl-substituted-pyridinium halide compounds for example1-butylpyridinium halide, benzylpyridinium halide, orhydrocarbyl-substituted-imidazolium halides, such as for example,1-ethyl-3-methyl-imidazolium chloride.

In one embodiment, the ionic liquid catalyst is an organic salt that ishygroscopic in nature and has a tendency to attract and hold watermolecules from the surrounding environment. With these ionic liquidcatalysts, in order to maintain the integrity of the ionic liquidcatalyst and its catalytic performance, the organic salts from which theionic liquid catalyst is synthesized, are thoroughly dried before thecatalyst synthesis, and moisture-free conditions are maintained duringthe alkylation reaction.

In one embodiment the ionic liquid catalyst is selected from the groupconsisting of hydrocarbyl-substituted-pyridinium chloroaluminate,hydrocarbyl-substituted-imidazolium chloroaluminate, quaternary aminechloroaluminate, trialkyl amine hydrogen chloride chloroaluminate, alkylpyridine hydrogen chloride chloroaluminate, and mixtures thereof. Forexample, the used ionic liquid catalyst can be an acidic haloaluminateionic liquid, such as an alkyl substituted pyridinium chloroaluminate oran alkyl substituted imidazolium chloroaluminate of the general formulasA and B, respectively.

In the formulas A and B; R, R₁, R₂, and R₃ are H, methyl, ethyl, propyl,butyl, pentyl or hexyl group, X is a chloroaluminate. In anotherembodiment, R, R₁, R₂, and R₃ are methyl, ethyl, propyl, butyl, pentylor hexyl group, and X is a chloroaluminate. In one embodiment the X isAlCl₄ ⁻, Al₂Cl₇ ⁻, or Al₃Cl₁₀ ⁻. In the formulas A and B, R, R₁, R₂, andR₃ may or may not be the same. In one embodiment the ionic liquidcatalyst is N-butylpyridinium heptachlorodialuminate [Al₂Cl₇ ⁻]. In oneembodiment the ionic liquid catalyst is 1-Ethyl-3-methylimidazoliumtetrachloroaluminate [emim⁺][AlCl₄ ⁻].

Products

Alkylate products that can be produced by this process include alkylatedaromatics and alkylated isoparaffins. The alkylate products can have abroad range of uses including, for example, as gasoline blendingcomponents, middle distillates, base oils, and petrochemical components.The gasoline blending components can have excellent properties,including high RONs and low RVP. The base oils can have excellentproperties, including low pour points, low cloud points, and variedviscosity indexes and kinematic viscosities. The middle distillates canhave unique branching properties, making some of them even suitable asjet fuel. Processes for making high quality alkylate gasoline blendingcomponents are described, for example, in earlier patent publications,including U.S. Pat. No. 7,432,408, U.S. Pat. No. 7,432,409, U.S. Pat.No. 7,553,999, U.S. Pat. No. 7,732,363, and US20110230692. Processes formaking base oils are described, for example, in U.S. Pat. No. 7,569.740,U.S. Pat. No. 7,576,252, U.S. Pat. No. 8,124,821, U.S. Pat. No.8,101,809, and Patent Application Nos. 12/966638 (filed Dec. 13, 2010)and Ser. No. 12/966,738 (filed Dec. 13, 2010) . Processes for makingmiddle distillates are described, for example, in U.S. Pat. No.7,923,593, U.S. Pat. No. 7,919,664, U.S. Pat. No. 7,955,495, and U.S.Pat. No. 7,923,594. Alkylated aromatic products and processes aredescribed in U.S. Pat. No. 7,732,651.

In one embodiment, the effluent from an alkylation reactor (40)comprises alkylate products (80). In one embodiment, a propane product,an n-butane product, and an alkylate gasoline blending component productare separated from an effluent from the alkylation reactor (40).

Extracted Conjunct Polymer Naphtha

In one embodiment, the process additionally comprises separating anextracted conjunct polymer naphtha (45) from an effluent from thehydrogenation reactor and blending the extracted conjunct polymernaphtha into an alkylate gasoline. The extraction of the extractedconjunct polymer naphtha (45) can be performed in a catalyst &hydrocarbon separator (500) or in a fractionation unit (200). Thehydrogenation of the conjunct polymer can improve the properties of theconjunct polymer made during the alkylation reaction such that it has asuitable boiling range and purity to be blended into high qualityalkylate gasoline. Blending the extracted conjunct polymer naphtha (45)in this way can greatly reduce waste disposal and equipment costs. Forexample, incineration, neutralization, and storage equipment can beeliminated from the alkylation process unit.

The extracted conjunct polymer naphtha (45) from the offgas of thehydrogenation reactor can have a final boiling point less than 246° C.(475° F). , such as having a boiling range distribution from 90° F. to474° F. (32° C. to 246° C.), from 95° F. to 460° F. (35° C. to 238° C.),from 100° F. to 450° F. (38 C to 232° C.), from 105° F. to 445° F. (41°C. to 229° C.), or from 110° F. to 440° F. (43° C. to 227° C.) . Thetest method used for determining the boiling range distribution is ASTMD86-11b. In addition, the extracted conjunct polymer naphtha can have alow sulfur content (e.g., from 0.05 wt % to 0.5 wt %) a low brominenumber (e.g., from <1 to 5), and a low chloride content (e.g., from 5ppm to 500 ppm), even without additional treatment.

In one embodiment, the process produces unique alkylate gasolineproducts that comprise the extracted conjunct polymer naphtha (45) thathas been hydrogenated and extracted from the hydrogenated effluent (10).In one embodiment, the alkylate gasoline comprises the extractedconjunct polymer naphtha (45) having a boiling point less than 246° C.(475° F.), and as further described above, extracted from the portion ofthe effluent (70).

The extracted conjunct polymer naphtha (45) from the offgas of thehydrogenation reactor can have a final boiling point less than 246° C.(475° F). , such as having a boiling range distribution from 100° F. to474° F. (38° C. to 246° C.), from 120° F. to 460° F. (49° C. to 238°C.), from 130° F. to 450° F. (54° C. to 232° C.), or from 140° F. to440° F. (60° C. to 227° C.). The test method used for determining theboiling range distribution is ASTM D2887-08. In addition, the extractedconjunct polymer naphtha can have a low sulfur content (e.g., from 0.05wt % to 0.5 wt %) a low bromine number (e.g., from <1 to 5), and a lowchloride content (e.g., from 5 ppm to 500 ppm), even without additionaltreatment.

In one embodiment, the process produces unique alkylate gasolineproducts that comprise the extracted conjunct polymer naphtha that hasbeen hydrogenated and extracted from the hydrogenated effluent (10). Inone embodiment, the alkylate gasoline comprises the extracted conjunctpolymer naphtha having a boiling point less than 246° C. (475° F.), andas further described above, extracted from the used alkylation catalyst.

Alkylation Process Unit

The alkylation process unit is one designed to conduct the processesdescribed herein. Process units performing these processes are shown inFIGS. 1, 3, 4, and 5. These process units all comprise a hydrogenationreactor and a fractionation unit fluidly connected to the hydrogenationreactor, a first connection between the fractionation unit and thehydrogenation reactor for transmitting at least a portion of thehydrogen gas to the hydrogenation reactor, and a second connectionbetween the fractionation unit and the alkylation reactor to transmit atleast a portion of the hydrogen chloride to the alkylation reactor. By“fluidly connected” it is meant that the connection provides a conduitwherein the contents move freely past one another and have the tendencyto assume the shape of their container; a liquid or gas.

In one embodiment, the fractionation unit comprises a gas/liquidseparator. In another embodiment, the fractionation unit comprises adistillation column. In yet another embodiment the fractionation unitcomprises a gas/liquid separator and an ionic liquid catalyst andhydrocarbon separator. The ionic liquid catalyst and hydrocarbonseparator can comprise a gravity separator,a coalescer,a liquid-liquidextractor,a distillation column, or combinations thereof.

In one embodiment, the alkylation process unit additionally comprises acompressor between the fractionation unit and the hydrogenation reactor.A compressor is a mechanical device that increases the pressure of a gasby reducing its volume. Examples of types of compressors arehermetically sealed, open, or semi-hermetic, centrifugal, diagonal,mixed-flow, axial-flow, reciprocating, rotary screw, rotary vane,scroll, diaphragm, and air bubble.

In one embodiment, the alkylation process unit additionally comprises athird connection between a product treatment unit and the secondconnection, wherein the stream comprising the hydrogen chloride,separated from the offgas of the hydrogenation reactor, is mixed with arecycled stream, from the product treatment unit, comprising a mixtureof a gaseous hydrogen chloride and a propane. The product treatment unitis used to separate and refine the products produced by the process andmay include further hydrotreatment and separation steps.

In one embodiment, the alkylation process unit additionally comprises aninlet wherein a hydrocarbon extraction solvent is fed to thefractionation unit or to a separator that is located between thehydrogenation reactor and the fractionation unit.

EXAMPLES Example 1 Ionic Liquid Catalyst Comprising Anhydrous MetalHalide

Various ionic liquid catalysts made of metal halides such as AlCl₃,AlBr₃, GaCl₃, GaBr₃, InCl₃, and InBr₃ could be used for the catalyticprocesses. N-butylpyridinium chloroaluminate (C₅H₅NC₄H₉Al₂Cl₇) ionicliquid catalyst is an example used in our process. The catalyst has thefollowing composition:

Wt % Al 12.4 Wt % Cl 56.5 Wt % C 24.6 Wt % H 3.2 Wt % N 3.3

Example 2 Alkylation of C₄ Olefin and Isobutane to Make AlkylateGasoline with and Without HCl Recycle

Evaluation of C₄ olefins alkylation with isobutane was performed in acontinuously stirred tank reactor using typical refinery mixed C₄ olefinfeed and isobutane. An 8:1 molar mixture of isobutane and olefin was fedto the reactor while vigorously stirring. An ionic liquid catalyst wasfed to the reactor via a second inlet port targeting to occupy 6 vol %in the reactor. A small amount of n-butyl chloride was added to produceanhydrous HCl gas. The average residence time (combined volume of feedsand catalyst) was about 4 minutes. The outlet pressure was maintained at200 psig and the reactor temperature was maintained at 95° F. (35° C.)using external cooling.

The reactor effluent was separated with a gravity separator into ahydrocarbon phase and an ionic liquid catalyst phase. The hydrocarbonstream was further separated into multiple streams: a C₃ streamcontaining HCl, an nC₄ stream, an iC₄ stream and an alkylate gasolinestream. The alkylate product had 94 Research Octane Number and 410 ° F.(210° C.) end point.

When the C₃ stream containing HCl was recycled to the alkylationreactor, we were able to lower the n-butyl chloride usage by 10% withoutaffecting alkylate gasoline properties. This confirmed that recoveringHCl with light hydrocarbon is an effective way to capture HCl and reuse.

Example 3 Isomerization of Olefin Feed, Alkylation, Regeneration ofIonic Liquid Catalyst by Hydrogenation and a Composition ofHydrogenation Reactor Offgas

A refinery C₃ and C₄ olefin stream from a Fluid Catalytic Cracking Unit(FCC unit) was isomerized with a Pd/Al₂O₃ catalyst at 66° C. (150° F.)and 250 psig in the presence of hydrogen to produce isomerized C₃ and C₄olefin feed with the composition shown in Table 1.

TABLE 1 Composition of Olefin Feed Composition Mol % Propane, C3 13.3Propylene, C3═ 25.4 1-Butene, 1-C4═ 2.3 2-Butene, 2-C4═ 16.2Isobutylene, i-C4═ 6.7 n-Butane, nC4 12.4 Isobutane, iC4 22.2 C5+ 1.6Sum 100.0

The isomerized olefin was alkylated with isobutane in a continuouslystirred tank reactor. An 8:1 molar mixture of isobutane and olefin wasfed to the reactor while vigorously stirring. An ionic liquid catalystwas fed to the reactor via a second inlet port targeting to occupy 6 vol% in the reactor. A small amount of n-butyl chloride was added toproduce anhydrous HCl gas. The average residence time (combined volumeof feeds and catalyst) was about 4 minutes. The outlet pressure wasmaintained at 200 psig and the reactor temperature was maintained at 95°F. (35° C.) using external cooling. The alkylation reactor effluent wasseparated to a hydrocarbon stream and an ionic liquid catalyst stream.The ionic liquid catalyst was recycled back to the alkylation reactorand the conjunct polymer level of the ionic liquid catalyst wasgradually increased.

Used ionic liquid catalyst containing 5 wt % conjunct polymer wasregenerated by passing the ionic liquid catalyst through a hydrogenationreactor under H₂ atmosphere. 100% pure hydrogen gas was used.Hydro-regeneration of the ionic liquid catalyst was operated at 350° F.(177° C.), 350 psig, 5000 scf H₂/bbl ionic liquid catalyst, and 0.2linear hourly space velocity (LHSV) in the presence of a hydrogenationcatalyst containing Pt and Pd. The hydrogenation reactor effluent wasseparated into offgas and separated liquid streams in a gas/liquidseparator as shown in FIG. 6. The separated liquid comprised regeneratedionic liquid catalyst and extracted conjunct polymer naphtha. At theseconditions, 80 wt % of the conjunct polymer in the ionic liquid catalystwas converted to light material and the regenerated ionic liquidcatalyst contained 1% conjunct polymer. The hydrogenation reactor offgasfrom the gas-liquid separation unit contained mostly H₂ and 6000 ppm ofHCl. The offgas also contained 95% H₂ and 5 vol % of C₃-C₆ lighthydrocarbons, while the bulk of light hydrocarbon was propane andisobutane. The purity of the hydrogen gas was dropped from 100% to 95%in one pass. In order to recycle the hydrogenation reactor offgas backto the hydrogenation unit, HCl and light hydrocarbon needed to beremoved.

This example clearly shows that it will be highly desirable to have anefficient way to remove and reuse the HCl and hydrocarbon in the offgas.By removing the HCl and hydrocarbon in the offgas, the hydrogen gas canbe recycled back to the hydrogenation reactor for repeated use. Forremoval of hydrogen chloride, a caustic treating method as shown in FIG.2, would result in substantial loss of HCl and light hydrocarbon.

The separated liquid stream from the hydrogenation unit was furtherseparated into the extracted conjunct polymer naphtha and regeneratedionic liquid catalyst. The regenerated ionic liquid catalyst wasrecycled back to the alkylation reactor for reuse.

Example 4 Improved HCl Recovery from Ionic Liquid Catalyst Hydrogenationwith Hydrocarbon Extraction Solvent

Used ionic liquid catalyst containing 4 wt % conjunct polymer from aalkylation reactor was regenerated by passing the ionic liquid catalystthrough a hydrogenation reactor under H₂ atmosphere. 100% pure hydrogengas was fed to the hydrogenation reactor. The hydrogenation reactor wasoperated at 350° F. (177° C.), 400 psig, 1500 scf H₂/bbl ionic liquidcatalyst, and 2.0 LHSV in the presence of a hydrogenation catalystcontaining Pt and Pd. The hydrogenation reactor effluent was separatedinto gas and liquid streams as shown in FIGS. 3 and 6. At theseconditions, 25 wt % of the conjunct polymer in the ionic liquid catalystwas converted to light hydrocarbon material, and the regenerated ionicliquid catalyst contained 3 wt % conjunct polymer. The hydrogenationreactor offgas from the gas-liquid separator contained mostly H₂ and1500 ppm of HCl. The offgas also contained 93 vol % H₂ and 7 vol % ofC₃-C₆ light hydrocarbons, while about 85-90 vol % of the lighthydrocarbon was propane and isobutane.

To demonstrate the concept of HCl extraction with hydrocarbon extractionsolvent, n-hexane solvent was added to the hydrogenation reactoreffluent at 2 and 4 times the volume of n-hexane to the ionic liquidcatalyst flow. Then the mixture was further separated with the sameseparator. The analysis results of the offgas stream are summarized inTable 1 below.

TABLE 2 HCl Content in Hydrogenation Offgas with Hydrocarbon ExtractionSolvent n-Hexane Flow Rate 2.0 4.0 vol/vol n-Hexane/ vol/vol n-Hexane/No Ionic liquid flow Ionic liquid flow n-Hexane to the Hydrogenation tothe Hydrogenation Flow Reactor Effluent Reactor Effluent HCl, ppm 1500500 300 H2 Purity, 93 94 95 vol % C3-C6, 7 6 5 vol %

As we added n-hexane solvent to the hydrogenation reactor effluent, thehydrogen chloride content in the offgas droppe)from 1500 ppm to 300 ppm.These results clearly suggested that the hydrogen chloride in the offgasstream can be extracted by adding hydrocarbon extraction solvent. Theabove set-up was a simple single stage separator. The extraction of thehydrogen chloride will improve further with multi-stage separationextractor, and possibly with counter-current flows of the two feeds tothe separator.

Example 5 An Integrated Process for H₂ Recycle and HCl Recovery fromIonic Liquid Catalyst Hydrogenation

This example shows an efficient H₂ purification/HCl recovery processusing the feeds to the alkylation reactor. One embodiment is shown inFIG. 5.

The offgas (50) separated from the hydrogenated effluent (10) from thehydrogenation reactor (100) was mixed with isomerized olefins (12) andisoparaffin feed (65) comprising make-up isobutane in the amounts asshown in Table 3. The combined mixture was separated in a fractionationunit (200) that was a distillation column to separate the mixture intoa) a gas fraction comprising a hydrogen gas (20), having low hydrogenchloride content, and b) a light hydrocarbon fraction comprising ahydrogen chloride (30). The light hydrocarbon fraction comprising ahydrogen chloride (30) contained the bulk (>90 wt %) of hydrogenchloride generated by the hydrogenation of used catalyst in the portionof the effluent (70) (in this example, ionic liquid catalyst). Thecompositions of the hydrogen gas streams before and after the HClextraction (i.e., Hydrogenation Unit Offgas [offgas (50)] and PurifiedGas Stream [gas fraction comprising a hydrogen gas (20)], respectively)are shown in Table 3.

The gas fraction comprising a hydrogen gas (20) (also referred to as thepurified hydrogen gas stream) was recycled back to the hydrogenationreactor (100) for regeneration of used catalyst in the portion of theeffluent (70), in this case a used ionic liquid catalyst. The used ionicliquid catalyst containing 5 wt % conjunct polymer was passed throughthe hydrogenation reactor (100) at 350° F. (177° C.), 450 psig, 5000 scfH₂/bbl ionic liquid catalyst using recycled hydrogen gas, and 0.2 weighthourly space velocity (WHSV) in the presence of a hydrogenation catalystcontaining Pt and Pd. At these conditions, 80 wt % of the conjunctpolymer in the used ionic liquid catalyst was converted to lightmaterial and the regenerated ionic liquid catalyst contained 1% conjunctpolymer. The hydrogenation reactor offgas [offgas (50)] from thegas-liquid separation unit [Separator (400)] contained 6000 ppm of HCland substantial amounts of hydrogen and light hydrocarbon.

TABLE 3 Composition of Recycle H₂ Stream and Alkylation Reactor Feedwith Recovered HCl HCl-Rich Hydro- Make-Up Purified Gas carbon Feed(Light Hydrogenation Isobutane Stream (Gas fraction hydrocarbon fractionUnit Offgas Isomerized (Isoparaffin comprising a hydrogen comprising ahydrogen (Offgas (50)) Olefins (12) feed (65)) gas (20)) chloride (30))Material Balance HCl, mole/day 0.605 0 0 0.024 0.581 H₂, mole/day 76 6 082 0.02 C₃ ⁼, mole/day 0 170 0 0.35 169 C₃, mole/day 12 74 44 16 113 C₄⁼, mole/day 0 215 0 0 215 iC₄, mole/day 13 165 243 22 398 nC₄, mole/day1 97 28 1 124 HCl Concentration HCl Recovery, wt % Source — — 4% 96%HCl, ppm 6000 — — 200 —

The results in Table 3 show that 96% of the hydrogen chloride from thehydro-regeneration offgas [offgas (50)] was recovered by our integratedprocess using a hydrocarbon extraction solvent (25). Thehydro-regeneration offgas [offgas (50)] had very high concentration ofhydrogen chloride, 6000 ppm. After the fractionation, the Purified GasStream [Gas fraction comprising a hydrogen gas (20)] contains only 200ppm of HCl and the Purified Gas Stream was recycled to the hydrogenationreactor (100). This process also produced a desirable light hydrocarbonfraction comprising a hydrogen chloride (30), with little residualhydrogen, and the light hydrocarbon fraction comprising a hydrogenchloride (30) was sent to the alkylation reactor (300).

This example showed that maximum recovery of hydrogen chloride could beachieved with extensive use of hydrocarbon extraction solvent where bothmake-up isobutane and olefin alkylation feeds are used to extracthydrogen chloride from the hydrogenation offgas. The efficient recoveryand recycle of hydrogen chloride greatly lowers the operating cost andreduces the quantity of make-up HCl that needs to be added to theprocess.

The transitional term “comprising”, which is synonymous with“including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, unrecited elements or methodsteps. The transitional phrase “consisting of excludes any element,step, or ingredient not specified in the claim. The transitional phrase“consisting essentially of limits the scope of a claim to the specifiedmaterials or steps “and those that do not materially affect the basicand novel characteristic(s)” of the claimed invention.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Furthermore, all ranges disclosed herein are inclusive ofthe endpoints and are independently combinable. Whenever a numericalrange with a lower limit and an upper limit are disclosed, any numberfalling within the range is also specifically disclosed.

Any term, abbreviation or shorthand not defined is understood to havethe ordinary meaning used by a person skilled in the art at the time theapplication is filed. The singular forms “a,” “an,” and “the,” includeplural references unless expressly and unequivocally limited to oneinstance.

All of the publications, patents and patent applications cited in thisapplication are herein incorporated by reference in their entirety tothe same extent as if the disclosure of each individual publication,patent application or patent was specifically and individually indicatedto be incorporated by reference in its entirety.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. Many modifications of the exemplaryembodiments of the invention disclosed above will readily occur to thoseskilled in the art. Accordingly, the invention is to be construed asincluding all structure and methods that fall within the scope of theappended claims. Unless otherwise specified, the recitation of a genusof elements, materials or other components, from which an individualcomponent or mixture of components can be selected, is intended toinclude all possible sub-generic combinations of the listed componentsand mixtures thereof.

It is claimed:
 1. An alkylation process unit, comprising: a. afractionation unit (200) for separating a hydrogen gas and a hydrogenchloride from an offgas (50) of a hydrogenation reactor (100) thatregenerates a used ionic liquid catalyst; and b. a first connectionbetween the fractionation unit (200) and the hydrogenation reactor (100)for transmitting at least a portion comprising the hydrogen gas to thehydrogenation reactor (100); and c. a second connection between thefractionation unit (200) and an alkylation reactor (300) to transmit atleast a second portion comprising the hydrogen chloride to thealkylation reactor (300).
 2. The alkylation process unit of claim 1,wherein the fractionation unit (200) is a distillation column.
 3. Thealkylation process unit of claim 1, additionally comprising an inletwherein a hydrocarbon extraction solvent (25) is fed to thefractionation unit (200) or to a separator (400) that is located betweenthe hydrogenation reactor (100) and the fractionation unit (200).
 4. Thealkylation process unit of claim 3, wherein the inlet is at a locationabove where the hydrogen gas and the hydrogen chloride are fed to thefractionation unit (200).
 5. The alkylation process unit of claim 1,additionally comprising a separator (400) between the hydrogenationreactor (100) and the fractionation unit (200).
 6. The alkylationprocess unit of claim 1, wherein the hydrogenation reactor (100)comprises a hydrogenation catalyst containing Pt and Pd.
 7. Thealkylation process unit of claim 1, wherein the used ionic liquidcatalyst is a chloroaluminate ionic liquid catalyst.
 8. The alkylationprocess unit of claim 1, additionally comprising an ionic liquidcatalyst and hydrocarbon separator (500) which separates the offgas (50)into a light hydrocarbon fraction comprising the hydrogen chloride (30),an extracted conjunct polymer naphtha (45), and an ionic liquid catalyststream (60).
 9. The alkylation process unit of claim 1, additionallycomprising a third connection between a product treatment unit and thesecond connection, wherein the second portion is mixed with a recycledstream, from the product treatment unit, comprising a mixture of agaseous hydrogen chloride and a propane.